“The score threshold that we developed based on women with breast cancer needs to be modified. It cannot be lifted and applied for men.”

“That means that the score threshold that we developed based on women with breast cancer needs to be modified. It cannot be lifted and applied for men,” said Xiao-Ou Shu, M.D., lead investigator on the study and Ingram Professor of Cancer Research at Vanderbilt University Medical Center.

Evaluating the Disparity

Shu and colleagues analyzed a National Cancer Database cohort of 848 male and 110,898 female breast cancer patients diagnosed between 2010 and 2014 with ER-positive, HER2-negative, stage I or II invasive breast cancer. Patients were classified as low-, intermediate- or high-risk based on traditional cutoffs (0-17, 18-30 and 31-100) and TAILORx cutoffs (0-10, 11-25 26-100).

Shu explained that while the average Recurrence Score in men was comparable to women (16.6 versus 17.2, respectively), score distribution was different with males occupying the extremes. “The proportion of patients with low and high Recurrence Scores was higher in male patients compared to female patients.”

The association of the Recurrence Score with mortality was also different between men and women. In men, Recurrence Score was associated with increased mortality until a score of 21, after which risk plateaued. In comparison, in female patients, mortality risk only began to increase with a score of 23.

Traditional cutoffs for Recurrence Score were not significantly associated with mortality in male patients. However, TAILORx cutoffs were, with both the intermediate (11-25) and high-risk groups having elevated mortality risk compared to the low-risk (≤ 10) group. In line with new guidelines, the study found that only female patients with a score of greater than 26, but not scores between 11-25, had higher mortality risk compared to those with a score of ten or less.

Distinct Biology

Accounting for roughly one percent of all breast cancers, male breast cancers are rare, generally understudied, and follow treatment recommendations based largely on evidence from female patients.

Shu says the results from this study and others support the idea that male breast cancer may have distinct biology and different prognostic factors compared to female breast cancer.

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Bio(s)

Xiao-Ou Shu, M.D., Ph.D., M.P.H., is Ingram Professor of Cancer Research and professor in the Department of Medicine at Vanderbilt University Medical Center. Her research focuses on the epidemiology of cancer and other non-communicable diseases.